Process of bending metal by wave formation



y 1962 G. L. HlTZ v 3,036,622

PROCESS OF BENDING METAL BY WAVE FORMATION Filed Feb. 28, 1958 2Sheets-Sheet 1 'G/FFOHD L. 19/ T2 INVENTOR.

May 29, 1962 G. L. HlTZ PROCESS OF BENDING METAL BY WAVE FORMATION FiledFeb. 2a, 1958 2 Sheets-Sheet 2 g/FFO/PD L. H/ TZ INVENTOR.

3,036,622 PRQCESS F EENDIL 1G METAL BY WAVE FORMATION Gifford L. Hitz,166i Bel Air Road, Les An eies, Calif. Filed Feb. 28, 1953, Ser. No.718,277 17 Claims. (Cl. 153-42) This invention relates generally tomechanical deformation of metal members such as plate, rod and tube, andmore particularly has to do with methods of forming bends, turns orcurvatures in such members, having the beneficial mechanical andmetallurgical effects of (1) producing short radius curvatures or bendsat any point along a metal member without stretching, cracking orthinning the outer radius section, or thickening, wrinkling ordistorting the inner radius section,

(2) providing in the bent or curved area of the metal member accurateretention of original dimensional characteristics, or close control ofchanges which may be desired in dimension or configuration,

(3) maintaining a preferred metal micro-structure, eliminating orminimizing residual tension stresses encountered in conventional bendingmethods, and minimizing and equally distributing desirable residualcompressive stresses, and

4) facilitating the bending or curving of metals which have smallelongation factors as no stretching is involved in the present method.

The invention is generally predicated upon an application of the rathernew concept that metal behaves differently under compressive loadingbeyond its yield point than under tensile loading beyond the yieldpoint, contrary to the wide-spread older view that for all practicalpurposes the effects of tensile and compressive loading upon the crystalstructure of metal can be treated as closely similar if not the same.

The present application of this newer concept concerns methods offorming turns or curves in elongated metal members, and is to bedistinguished from older known methods of deforming metal to producebends, wherein proper recognition was not given to the difference inbehavior of the crystal structure of metal loaded in compression asdistinct from tension. Thus in prior processes the metal was deformedeither hot or cold in a manner calculated to produce a resultantconfiguration with attention given to grain structure, rather than tothe arrangement of atoms in the crystal or lattice structure of themetal. As a result, metal being bent (particularly at temperatures belowthat required for recrystallization) was subject to undesirable andnon-uniform strain hardening, cracking and distortion, and also, theforce required to advance the metallic member relative to the deformingdies was undesirably great in order to overcome the resistance to memberbending, which is related to the amount, direction and character ofmetal movement, and to the degree of strain hardening of the metal beingbent.

The present novel method represents an application of the principle thatthe bonding forces acting to hold int-act metals of a crystallinecharacter, and the disposition of crystal imperfections and atomicdislocations within the metal are affected by compressive loading of themetal beyond its yield point in a manner permitting more deformation orplastic flow before the metallic structure reaches a condition wherefurther deformation would cause rupture, than if the metal were loadedin tension.

Applying the theory that dislocations in the atomic structure ofcrystalline metals are a prime factor permitting such metals to beplasticly deformed at temperatures below that of recrystallization, andthat stretching such metals (as is typical of conventional bendingtechniques) tends to concentrate the dislocations from ceri be tain slipplanes at crystal or grain boundaries, then it becomes obvious that thestretching force being applied is able to utilize only a comparativelylimited number of slip planes before this concentration of dislocationscauses cracking. Visible striations in metal loaded in tension beyondthe yield point illustrate the concentration of slippage and strain in afew separated areas.

in bending by wave formation, continuous and uniformly increasingcompressive force within the crystal structure of the metal causes thepropagation of dislocations in a spiral effect within each crystal andthus makes use of a much larger number of slip planes than would beutilized if the metal were being loaded in tension.

Basically, the method of the present invention contemplates advancing anelongated metal member into compressive engagement with forming bodiesarranged in such relation that the metal is not subjected to tensionloading beyond the yield point, but is deformed beyond the yield pointby compressive loading. The preferred steps of the method includecompressively advancing the elongated member in the elongationdirection, retarding metal advancement at one side of the member (whichis to become the inner radius side) so that retarded metal is compressedbeyond its yield point, and is guided and gathered into a protrusion ofincreased cross sectional area at said side, and consecutivelyimpressing on said inner radius side the true curvature of the finishedbend, this impressing being done at a tangent angle opposite to that ofthe finished bend, and the protrusion, and without unduly restrictingthe movement of the opposite side of the member (the outer radius side),and subsequently compressively side loading the member beyond its yieldpoint and at an advanced opposite side (the outer radius side) to theprotrusion, in a direction toward retarded metal at the member innerradius side advancing forwardly of the protrusion, so that the outerradius portion of the member is permanently turned away from the initialdirection of advancement, and the member is reduced from the enlargedcross sectional area and thickness created by the protrusion, to theoriginal (or desired) cross-sectional area and configuration.

The application of metal retarding and side loading forces in effectproduces what may be termed a protrusion or wave-shaped gathering ofmetal at one side of the member. In the case of plate or rod theretarding effect is preferably carried out by compressing one side ofthe advancing member so that not only is the metal retarded at said sidebut is subsequently compressively side loaded at the forward side of theprotrusion beyond the metal yield point and in a direction toward themember opposite side. Thus, the retarded metal is compressively directedtoward the opposite side of the plate or rod. In the case of tubing orpipe the retardation effect is better accomplished by utilizing amandrel with a protrusion formed thereon to guide one side of theadvancing tube into the desired standing wave or protrusionconfiguration. The protrusion on the mandrel may be fixed or solid, orit may be retractable (collapsible) to facilitate entry and withdrawalof the mandrel, or it may consist of hydraulic pressure, limitedinternally by seals applying against the inside of the tube. In thishydraulic arrangement, a concave die is required on the outside of thetube protruberance to control the size and shape thereof.

It should be noted from the above description of the method that livecoordinated actions are utilized, none of which are common withconventional bending or forming practices. These actions can beseparately described as follows:

(1) Retarding and shortening the inner radius section of the member byformation of a protrusion,

(2) coincidentally with (l), gathering metal in the protrusion area tohave an increased total cross sectional 3 area from which to latercompressively form the bend or curve,

(3) sequentially further retarding and setting back the inner radiussection of the member, by arranging the protrusion and the radius die sothat a devious or indirect route is followed by the metal of the innerradius section,

(4) Coincidentally with (3), preforming the actual inside radius of thebend at a tangent angle opposite to the final angle of the bend, andwhile the outside radius section is unrestricted,

(5) sequentially, applying compressive force, in three directionssimultaneously, to the outer radius section, to cause accelerated metalflow in that section.

A further explanation of these actions is as follows:

1) Retarding at prtrusi0n.-When the side of the metal member which is tobecome the inner radius side of the completed bend, is guided orconfined by suitable toolin members into the form of a standing wave orprotrusion, resistance to the compressive advancement of the metalmember by the tooling or die member, causes the metal of the innerradius side to widen out, and gather up, and consequently to slow downbefore passing beyond the protrusion, thus effecting a setting back ofthat side relative to the opposite side, which is to become the outerradius side of the bend.

(2) Increase in total cross-secti0nal.-Additionally, the widening outand gathering up of metal in the protrusion serves to create anincreased total cross-sectional area in the metal member, from whichmetal can later be directed compressively, under controlledextrusion-type orifice conditions, into the desired bend or curveconfiguration, Without reducing the member below its original dimensions.

(3) Further retarding inner radius side by creating a devious path-Afurther retarding of the inner radius side relative to the opposite sideis developed by positioning the radius die immediately beyond theprotrusion so that a further change is caused in direction of the pathof travel taken by the inner radius side of the metal rnember, whichrequires that this side must travel a longer distance than the oppositeside.

(4) Preforming inner radius.l ressures controlled by the position ofguide blocks, guide rolls, or mandrel relative to the radius die,compressively create the sharp curvature of the inside radius of thebend, at a tangent angle opposite to the final angle of the bend, thisbeing accomplished while the guide members, mandrel, radius die andother tooling members are so positioned that the opposite side is freeto continue in a straight path or actually joggle slightly away from thefinal direction of bending, thus permitting this critical part of thebend to be formed wtihout wrinkling, thickening, or distortion. Thepressure caused by the resistance of the metal to the changed direct-ionaugments the force exerted by the guide roll or mandrel suificiently tocreate the inside radius configuration on the metal without causingappreciable diminishing of the cross-sectional area at this point.

Increasing rate of metal flow in outer radius section by multipleangular forces-43y placing a pressure die angularly in the path oftravel of the metal member, and in proper relationship to the radiusdie, the outer radius section of the metal member is turned in thedirection of the bend, and the cross-sectional area of the member isreduced back down to original size (or such other dimension as may bedesired within practical limits). This restrictive change in directionof the member results in the metal of the outer radius section beingacted on simultaneously by three compressive forces, as follows:

(a) From directly behind, as a result of the movement of the meansadvancing the member.

(b) From the restrictive, angularly placed pressure die, which is actingto turn the metal member at an angle relative to the original directionof member movement, and reduce it in cross-sectional area,

(c) From the thickened middle section of the member, which was createdby the forming of the protrusion, and which is now impelled by the innerradius section in a direction causing this metal to impinge on theredirected course of the metal of the outer radius section. The inherentstiffness of the metal acts to prevent this middle section metal fromreturning to rejoin the inner radius section (from which it was evolvedin the formation of the protrusion) and carries it toward the outerradius section, of which it becomes a contiguous part. The action of thethree compressive forces just described cause a relative increase in therate of travel of the metal in the outer radius section, in somewhat thesame man ner as a cone-shaped charge in explosive practice causes anincreased speed of explosive force. known as the Monroe effect. Thecoordinated action of the three forces and the flow pattern cause anincreased flow rate, while the forward motion of the metal of the middlesection acts to prevent thinning. The result is that the outer radiussection of the completed bend has been lengthened compressively withcontrolled dimensional characteristics.

Refinements of the new method include supporting the member opposite theprotrusion to prevent side deflec tion thereof, exerting compressiveside loading on the member in a direction toward the axis about whichthe member is turned or bent and at a preferred angle with respect to anormal to the direction of initial member advancement, the normalextending through that axis, compressively side loading the permanentlyturned portion of the advancing member to control the degree of finalturning, and pulling the permanently turned portion of the advancingmember around the axis of turning with sufficient tension normally belowthe yield point of the metal, to control the size of the protrusionformed by the metal, and to control the radius of the finished bend.

Other features and objects of the invention, as well as the details ofan illustrative embodiment, will be more fully understood from thefollowing detailed description of the drawings, in which:

FIG. 1 is an elevation showing an elongated metallic plate being formedor bent in accordance with the methods of the invention;

FIG. 2 shows sections through plate, rod and tube members which may bebent or turned in accordance with the present methods;

FIG. 3 is an enlarged elevation illustrating the application ofcompressive loading on the metal member and the path taken by the metalof the member as it is bent or turned;

FIG. 4 is a view similar to FIG. 1 showing a tube being bent or turnedby somewhat modified apparatus;

FIG. 5 is a section taken on line 55 of FIG. 4;

FIG. 6 is a view similar to FIG. =1 illustrating another modified methodof bending or turning a plate member; and

FIG. 7 is a section showing tube being engaged by a concavely curvedforming means.

In FIG. 1, the elongated metal member 10 is shown being compressivelyadvanced in the direction of arrow 11 by the plunger 12 hydraulicallyactuated by pressure within cylinder 13; the member 10 comprising forexample a plate as shown at 14 in FIG. 2. The principles of the presentmethod are equally applicable to rod and tube members shown at 15 and 16in FIG. 2, and are discussed in terms of a plate as regards FIGS. 1 and3 merely for purposes of illustration.

The plate member 10 is advanced between what may be termed a radius roll17 about the axis 18 of which the member is permanently turned or bent,and a larger pressure roll 19 opposite from radius roll 17 in thedirection of initial member advancement, as will be described. The metalmember is first acted upon by the radius roll which retards advancementof the metal at the upper side 20 of the member so that the retardedmetal is compressed beyond its yield point and protrudes at 21 in theform of a standing wave. In addition, the radius roll compres sivelyside loads the forward slope 22 of the protrusion beyond its yield pointand in a direction toward the directly opposite side portion 23 of themetal member with the result that the retarded metal at the forwardslope of the protrusion is laterally compressively displaced. In thecase of tube members, the retarded metal is thus displaced in directionsas shown by arrows 24 in FIG. 2 toward the opposite outer side portion23 of the member.

The member opposite or underside 25 in general advances in the directionof member elongation over a sup port roll 26 which does notcompressively load said side beyond its yield point, following whichsaid side is compressively loaded by the forming roll 19 beyond themetal yield point and in a direction toward the radius roll 17 and theretarded metal 27 at the member side advancing forwardly of theprotrusion 21, so that the loaded portion 28 of the member ispermanently turned away from the direction of advancement 11.

Extending the description to FIG. 3, stationary dies 29 and 129 havingfiat surfaces 3t? engaging the outer side 25 of the metal member aresubstituted for the rolls 19 and 26 but otherwise the elements remainthe same as described in FIG. 1, and the method remains the same in bothFIGS. 1 and 3. Compression induced relative slippage of a typical blocksection of metal generally indicated at 31, during formation of theturn, is illustrated by the subsequent relative locations of greatlyenlarged body centered cubic crystals 131 of the metal in the blocksection as it progresses around the bend. Thus, broken line IR-OR showsa reference alignment of metal molecules at the front of the blocksection sufficiently in advance of the protrusion 21 that said line isnormal to the direction of application of the force F parallel to theinitial advancement direction indicated at 11. Broken line IR ORillustrates a subsequent position of the front, the metal at outerradius point 0R being relative ly advanced beyond the metal at 1R at theupper side 24 of the member. Thus, the IR, metal is shown as beingrelatively retarded by the compressive action of the radius roll 17 uponthe forward slope 22 of the protrusion 21, the compressive gathering ofretarded metal forming the protrusion in wave shape as shown. With thesize of the protrusion controlled, as will be described, it will remainas a standing wave in the metal.

The broken line OR IR extending between the lower and upper sides of themember 10 as it is fed through the restricted opening between the roll17 and die 2? shows that the metal at the member outside has greatlyadvanced relative to the retarded metal at the upper side of the memberand relatively more than the degree of advancement illustrated by lineOR lR the broken line O-R IR also shows that the outside of the blocksection front has disengaged the die 39 while the inside of the frontremains compressively engaged by the radius roll. Arrows 33 and 34illustrate the application of side loading exerted by the radius rolland the die on the upper and lower sides on the metal member 10 andproductive of formation of the turn 32.

It will be observed in FIGS. 1 and 3 that the thickness of the memberbetween the upper and lower outer sides thereof at the turn 32 and atthe initially nondeformed advancing portion of the member areapproximately the same, showing that the member has been turned or bentto a predetermined degree without reducing its overall thickness. At thesame time, deformation of the member has been carried out as explainedin the introduction, so as to squeeze out and accelerate the flow ofmetal at the outer radius side of the member through creation of amiddle section 68 at the protrusion 21 that squeezes against and becomesa contiguous part of the flattened outer radius section 61, broken line62 demarking the boundary therebetween by the application of compressiveloading so as to provide uniformly distributed metal motion with minimumstrain concentrations or work hardening of the metal. By varying theclearance space between the forming die 29 and the radius roll 17, thethickness (or diametric size) of the member may be controlled to lessthan, or slightly more than, the original thickness or size. in the caseof plate or rod, initial starting or formation of the protrusion 21required for retarding the metal at the upper side 26 of the member maybe carried out by decreasing the relative distance between the radiusroll and the die 23 when the member forward end is initially fed betweenthese forming devices, and then when the protrusion has been formed theradius roll may be retracted slightly away from the die, or vice versa,so as to maintain the desired thickness relationship of the member atthe formed turn 32 and at the undeformed portions of the member.

By the present method it is possible to lengthen compressively the outerradius side of the member by without thinning of the overall memberthickness at the resultant bend. If for example 30% thinning istolerable, then it is possible to lengthen the outer radius side by200%, all the bending forces being compressive.

In FIG. 1, the permanently turned portion 32 of the member 10 is shownto have a curvature of less than that of the radius roll, with a slightgap 34 developing between the turn and said roll as the turn proceedsaround the roll. A pair of control rolls 35 are shown compressivelyloading the outer side of the permanent turn so as to accurately controlthe final radius or curvature of the turn. In practice, the approximateoptimum direction of application of side loading by the die 29 or roller19 so as to produce the turn 32; is such that its angularity with anormal to the initial member advancement direction extending through theaxis 18 about 28, as shown in FIG. 3. However, this angle may vary withdifferent metals, thicknesses, ductility, degree or radius of bend, fromabout 10 to about 50.

The control of the size of protrusion 31 may be obtained by positivelydriving the radius roll 17 or the fenning roll 19 or die 29 substitutedtherefor, or both. Alternatively, the forward end portion of the member10 turning around the radius roll may be clamped at 44 by an arm 41 thatis positively driven as shown in FIG. 6 to pull the bend or turn aroundthe axis of the radius roll 17. FIG. 6 also illustrates a plate it}being driven in the direction of advancement thereof by a large numberof power rollers 42 disposed at intervals along the direction of plateadvancement both above and below the plate to frictionally engage itsopposite sides. The use of a number of rollers 42 for advancing theplate permits a reduction in the amount of normal force required to beexerted by each roller against the side of the plate and below the yieldpoint of the plate metal, without sacrificing the desired total forceexerted on the plate in the direction of advancement for securing theformation of the turn 32. A forming shoe 43 substituted for a formingroller constitutes the final change in the turn forming apparatus, theshoe having a curved forming surface 44 for exerting compressive loadingon the outside of the plate over a considerable portion thereof.

In FIG. 4, a tube 45 is shown being subjected to the turn formingoperation or method constituting the present invention. A protrusion 21is formed at the tube upper side by the guiding action of a mandrel 46extending within the tube and having a suitable guide protrusion 47. Themandrel protrusion does not act to stretch the tube metal beyond itsyield point but merely guides it as the metal gathers compressively toform the desired shaped protrusion. In addition, the forward end 49' ofthe mandrel guides the tube metal being compressively side loaded by aplatform die 59 serving the same function as the forming roller 19 inFIG. 1. This platform is mounted on rollers 51 so that it moves with thetubing being permanently turned and thereby eliminates sliding fractionwhich would otherwise exist at the platform and tubing interface.Finally, a pair of control rollers 35 compres- 7 sively side load thetubing in the manner discussed in FIG. 1.

So as to properly shape the tubing being permanently turned or bent bythe action of the radius roller 17 and the platform, each of theselatter elements may have concavely curved or specially shaped, surfaces53 with curvature similar to that of the tubing curvature as shown inFIG. 7.

I claim:

1. The method of forming a turn in an elongated metal Work member havingelongated opposite sides, that includes advancing the member in saidelongated direction, retarding metal advancement at one side of themember traveling in said direction relative to metal advancement at theopposite side thereof so that retarded metal is compressed beyond itsyield point and protrudes at said one side, and side loading the memberbeyond its yield point and at the advanced opposite side thereof in adirection toward retarded metal at said member one side forwardly of theprotrusion so that the member is permanently turned away from saiddirection of advancement, and maintaining the protrusion while themember is advanced and side loaded to produce said turn and so that theprotrusion exists only at said one side of the member at a locationtherealong beyond which the advancing member commences to turnpermanently.

2. The method of forming a turn in an elongated metal work member havingelongated opposite sides, that includes compressively advancing themember in said elongated direction, retarding metal advancement at oneside of the member traveling in said direction relative to metaladvancement at the opposite side thereof so that retarded metal iscompressed beyond its yield point and protrudes at said one side, sideloading the forward portion of the protrusion beyond its yield point andin a direction toward said member opposite side, and side loading themem ber beyond its yield point and at the advanced opposite side thereofin a direction toward retarded metal at said member one side forwardlyof the protrusion so that the member is permanently turned away fromsaid direction of advancement, and so that the turned member hasthickness less than the maximum member thickness at said protrusion, andmaintaining the protrusion while the member is advanced and side loadedto produce said turn and so that the protrusion exists only at said oneside of the member at a location therealong beyond which the advancingmember commences to turn permanently.

3. The method of forming a turn in an elongated metal member havingelongated opposite sides, that includes simultaneously compressivelyadvancing the member in said elongated direction, retarding metaladvancement at one side of the member traveling in said directionrelative to metal advancement at the opposite side thereof so thatretarded metal is compressed beyond its yield point and protrudes atsaid one side, side loading the member beyond its yield point and at theadvanced opposite side thereof in a direction toward retarded metal atsaid member one side forwardly of the protrusion so that the member ispermanently turned away from said direction of advancement, and pullingthe permanently turned portion of said member with sufficient tensionbelow the yield point of the metal to control the size of saidprotrusion, and maintaining the protrusion while the member is advancedand side loaded to produce said turn and so that the protrusion existsonly at said one side of the member at a location therealong beyondwhich the advancing member commences to turn permanently.

4. The method of forming a turn in an elon ated metal member havingelongated opposite sides, that includes advancing the member in saidelongated direction, rolling one side of the advancing member travelingin said direction to retard metal advancement at said side relative tometal advancement at the member opposite side so that retarded metal iscompressed beyond its yield point and protrudes at said one side andalso to side load compressively the forward portion of said protrusionbeyond its yield point and in a direction toward said member oppositeside for laterally displacing said retarded metal, and side loading themember beyond its yield point and at the advanced opposite side thereofin a direction toward retarded metal at said member one side forwardlyof said protrusion so that the member is permanently turned away fromsaid direction of advancement, and so that the turned member hasthickness less than the maximum member thickness at said protrusion andmaintaining the protrusion while the member is advanced and side loadedto produce said turn and so that the protrusion exists only at said oneside of the member at a location therealong beyond which the advancingmember commences to turn permanently.

5. The method of claim 4 including supporting the opposite side of saidmember relatively in advance of the protrusion.

6. The method of claim 4 comprising exerting said side loading on themember advanced opposite side in a direction toward an axis about whichsaid member is turned.

7. The method of claim 6 comprising exerting said side loading at anangle of between 10 and 50 degrees with respect to a normal to themember initial advancement direction extending through said axis.

8. The method of claim. 4 in which side loading said opposite side ofthe advancing permanently turned portion of said member is directedgenerally toward an axis about which said member is turned to accuratelycontrol the degree of final turning.

9. The method of claim 4 including pulling the permanently turnedportion of the advancing member around the axis of turning withsufficient tension below the yield point of the metal to control thesize of said protrusion.

10. The method of claim. 4 including compressively advancing said memberby compressively rolling without permanently deforming said oppositesides thereof in said direction and in advance of said protrusion.

11. The method of forming a turn in an elongated metal plate havingelongated opposite sides that includes advancing the plate in saidelongated direction, rolling one side of the advancing plate travelingin said direction to retard metal advancement at said side relative tometal advancement at the plate opposite side so that retarded metal iscompressed beyond its yield point and protrudes at said one side andalso to side load the forward portion of said protrusion beyond itsyield point and in a direction toward said plate opposite side forlaterally displacing said retarded metal, and side loading the platebeyond its yield point and at the advanced opposite side thereof in adirection toward retarded metal at said plate one side forwardly of saidprotrusion so that the plate is permanently turned away from saiddirection of advancement and maintaining the protrusion while the plateis advanced and side loaded to produce said turn and so that theprotrusion exists only at said one side of the plate and at a locationtherealong beyond which the advancing plate commences to turnpermanently.

12. The method of forming a turn in an elongated metal rod havingelongated opposite sides that includes advancing the rod in saidelongated direction, rolling one side of the advancing rod traveling insaid direction to retard metal advancement at said side relative tometal advancement at the rod opposite side so that retarded metal iscompressed beyond its yield point and protrudes at said one side andalso to side load the forward portion of said protrusion beyond itsyield point and in a direction toward said rod opposite side forlaterally displacing said retarded metal, and side loading the rodbeyond its yield point and at the advanced opposite side thereof in adirection toward retarded metal at said rod one side forwardly of saidprotrusion so that the rod is permanently turned away from saiddirection of advancement and maintaining the protrusion while the rod isadvanced and side loaded to produce said turn and so that the protrusionexists only at said one side of the rod at a location therealong beyondwhich the advancing rod commences to turn permanently.

13. The method of forming a turn in an axially extending metal tubehaving elongated opposite sides, that includes advancing the tube insaid axial direction, rolling one side of the tube traveling in saiddirection to retard metal advancement at said side relative to metaladvancement at the tube opposite side so that retarded metal iscompressed beyond its yield point and forms an enlarged protrusion atsaid one side and also to load the forward portion of said protrusionbeyond its yield point and in a direction toward said tube opposite sidefor laterally displacing said retarded metal, and side loading the tubebeyond its yield point and at the advanced opposite side thereof in adirection toward retarded metal at said tube one side forwardly of saidprotrusion so that the tube is permanetly turned away from saiddirection of advancement and maintaining the protrusion while the tubeis advanced and side loaded to produce said turn and so that theprotrusion exists only at said one side of the tube at a locationtherealong beyond which the advancing tube commences to turnpermanently.

14. The method of claim 13 including supporting the bore of said tube atsaid protrusion for retardation of said metal by compressive rollingthereof.

15. The method of forming a short radius bend at a selected locationalong an elongated metal member having elongated opposite sides withoutstretching or thinning the outer radius section, or thickening,wrinkling or distorting the inner radius section, and wherein originalcross-sectional dimensional characteristics can be retained or otherwisecontrolled as desired, and wherein a preferred metal microstructure canbe maintained, free from undesirable residual tension stresses, and withdesirable, uniformly distributed, minimum residual compressive stresses,that includes advancing the metal member in said elongated directionprincipally by applying mechanical force in the direction of memberadvancement and at a point preceding the area in which the forming is tobe done, retarding advancement of one side of the metal member relativeto advancement of the opposite side of the member in such a manner thatthe retarded metal is compressed beyond its yield point and gathers atsaid one side into a protrusion of increased metal cross-sectional area,further advancing the metal member in the same continuing elongateddirection and side loading the advanced opposite side of the metalmember beyond the yield point of the metal and in a direction toward theretarded metal of the member one side forwardly of the protrusion,further advancing the metal member and continuing to side load the saidadvanced opposite side so that said opposite side and also the one sideare guided into a restricted opening of less cross dimension than thecross-dimension which the metal member acquired during said gathering,and further advancing the metal member through said restricted openingand compressing said member therein to accelerate member advancement atsaid opposite side relative to said one side, and maintaining theprotrusion while the member is advanced and side loaded to produce saidturn and so that the protrusion exists only at said one side of themember at a location therealong beyond which the advancing membercommences to turn permanently.

16. The method of forming a short radius bend at a selected locationalong an elongated metal member having elongated opposite sides withoutstretching or thinning the outer radius section, or thickening,wrinkling or distorting the inner radius section, and wherein originalcross-sectional dimensional characteristics can be retained or otherwisecontrolled as desired, and wherein a preferred metal micro-structure canbe maintained, free from undesirable residual tension stresses, and withde sirable, uniformly distributed, minimum residual compressivestresses, that includes advancing the metal member in said elongateddirection principally by applying mechanical force in the direction ofmember advancement and at a point preceding the area in which theforming is to be done, retarding advancement of one side of the metalmember relative to advancement of the opposite side of the member insuch a manner that the retarded metal is compressed beyond its yieldpoint and gathers at said one side into a protrusion of increased metalcross-sectional area, subsequently further advancing the metal memberand side loading the said one side at a point contiguous with and beyondthe protrusion, so that the metal of said one side is compressed beyondits yield point into a curved configuration similar to the curvedconfiguration required for the inner radius side of the completed bend,allowing the member opposite side to advance free of side loadingopposite the protrusion, further advancing the metal member in the samecontinuing elongation direction and, subsequent to preforming the saidone side, side loading the advanced opposite side of the metal memberbeyond the yield point of the metal and in a direction toward theretarded metal of the member one side forwardly of the protrusion,further advancing the metal member and continuing to side load theadvanced opposite side so that said opposite side and also the one sideare guided into a restricted opening of less cross-dirnension than thecross-dimension which the metal member acquired during said gathering,and further advancing the metal member through said restricted openingand compressing said member therein to accelerate member advancement atsaid opposite side relative to said one side and maintaining theprotrusion while the member is advanced and side loaded to produce saidturn and so that the protrusion exists only at said one side of themember at a location therealong beyond which the advancing membercommences to turn permanently.

17. The method of forming a short radius bend at a selected locationalong an elongated metal member having elongated opposite sides withoutstretching or thinning the outer radius section, or thickening,wrinkling or distorting the inner radius section, and wherein originalcross-sectional dimensional characteristics can be retained or otherwisecontrolled as desired, and wherein a preferred metal micro structure canbe maintained, free from undesirable residual tension stresses, and withdesirable, uniformly distributed, minimum residual compressive stresses,that includes advancing the metal member in said elongated directionprincipally by applying mechanical force in the direction of memberadvancement and at a point preceding the area in which the forming is tobe done, side loading one side of said member so that the metal of saidone side is compressed beyond its yield point into a curvedconfiguration similar to the curved configuration required for the innerradius side of the completed bend, allowing the member opposite side toadvance free of side loading opposite the protrusion, further advancingthe metal member in the same continuing elongation direction and,subsequent to preforrning the said one side, side loading the advancedopposite side of the metal member beyond the yield point of the metaland in a direction toward the retarded metal of the member one sideforwardly of the protrusion, further advancing the metal member andcontinuing to side load the said advanced opposite side so that saidopposite side and also the one side are guided into a restricted openingof less cross-dimension than the crossdimension which the metal memberacquired during said gathering, and further advancing the metal memberthrough said restricted opening and compressing said member therein toaccelerate member advancement at said opposite side relative to said oneside and main- 1 1 taining the protrusion while the member is advancedand side loaded to produce said turn and so that the protrusion existsonly at said one side of the member at a location therealong beyondwhich the advancing member commences to turn permanently.

Williams May 1, 1934 Snell Apr. 9, 1935 12 Taylor Nov. 28, 1939 TaylorNov. 12, 1940 Lignian June 10, 1941 Kepler Feb, 2, 1943 Ottie Aug. 17,1943 FOREIGN PATENTS Germany Feb. 13, 1933 Great Britain July 21, 1932Great Britain Nov. 9, 1936

